Polybrominated biphenyls (PBB) have been reported to produce clinical signs of neurological toxicity in humans and neurobehavioral deficits in rats in relatively short exposures. The present work was intended to assess neurobehavioral consequences of chronic (six month) exposure to a commercial mixture of PBB (Firemaster FF-1). Rats received 0.3, 1.0, or 3.0 mg/kg body weight of FF-1 or corn oil vehicle. Both male and female rats were tested in a battery designed to screen for neurobehavioral dysfunction. Tests included: body weight, motor activity, forelimb grip strength, hindlimb strength, startle to air puff, and rectal temperature. Shock escape latencies and acquisition of shock avoidance were tested at the end of six months of dosing.